Immune response to chlamydial genital tract infections and its effect on pathogenesis will be studied in experimental animal models. The role of humoral and cell-mediated immunity in resistance (immunity) to challenge will be explored in the guinea pig using the agent of guinea pig inclusion conjunctivitis (GPIC), a Chlamydia psittaci agent. The genital secretory immune system will be examined in detail to define its role in recovery mechanisms and subsequent resistance. The effect of antibiotic therapy on immune response will be documented and susceptibility to reinfection following therapy investigated. The feasibility of use of an inactivated GPIC vaccine administered in the genital tract will be tested. Using selective immunosuppression by cyclophosphamide, salpingitis will be produced and followed for effect on fertility. A new model employing mice and the agent of mouse pneumonitis (MoPn) developed in this laboratory will be further explored. MoPn is a Chlamydia trachomatis agent and is the only animal counterpart of the agent causing human genital infections. Studies will involve sexual transmission, transmission to new born, development of immunity, and function of humoral and cell-mediated immunity.